radar detector

Definition of radar detector

1: a device designed to alert the operator of a vehicle when it has been targeted by a radar beam (as from a police officer's radar gun)
After fastening a radar detector to the windshield, he slaloms through traffic at illegal speeds for the seven-mile trip to Chrysler's Styling Dome …— Alex Taylor IIIHe chuckled about the radar detector in his big station wagon … saying he never drove faster than 60 anyway.— Stephan Wilkinson

2: radar gunThe officer's radar detector recorded the vehicle speed between 55 and 60 mph, with the speed reaching 70 mph at one point on the 55 mph-limit roadway.— Robin Baumgarn